PHOENIX -- Maricopa County Sheriff Joe Arpaio is as popular and polarizing as ever, evident in the amount of outside interest and influence focused on his race for a sixth consecutive term.

Arpaio, who became a national icon in the illegal-immigration enforcement movement during the past decade, has raised as much as 80% of his campaign's $8 million from out-of-state donors. In addition, he has garnered support from political-action committees raising money in his name and occasionally spending it on his behalf.

That is hardly a new development. But in a twist not seen in the sheriff's prior electoral battles, Arpaio's main opponent, retired Phoenix police Sgt. Paul Penzone, is also benefiting from factions outside Arizona that are interested in the race, including an independent political-action committee that received $500,000 from labor groups spending money on materials and activities aimed at unseating Arpaio.

Immigration, the sheriff's signature issue, is responsible for attracting much of the national money pouring in on both sides of the race, said Bruce Merrill, a longtime Arizona political scientist and pollster.

"Joe's become the focus of the Senate Bill 1070 groups. Since (ousted Arizona Senate President) Russell Pearce is now gone, Joe is really kind of the face of that whole movement," Merrill said. "This race is just heavily influenced by that, and the money that the sheriff has been able to raise may well keep him in office."

Translating out-of-state support into votes in Maricopa County is the challenge for Arpaio's campaign. It spent more than $700,000 from mid-August to mid-September promoting the sheriff's legacy via television ads, according to the most recent campaign-finance reports. More recently, the campaign has inundated local airwaves with ads attacking Penzone over allegations made by his ex-wife during their 2003 divorce.

The anti-Arpaio groups, by contrast, are focused on getting out the vote.

Campaign for Arizona's Future, a political-action committee targeting Arpaio, has been funded by $500,000 from the AFL-CIO and UNITE HERE, a hotel- and hospitality-workers' union. The labor groups' donations nearly match what Penzone's own campaign has raised from contributors so far.

Anti-Arpaio money has largely been spent on salaries for in-state workers, meals and supplies, according to campaign-finance reports.

Campaign for Arizona's Future also paid for a mailer this month reminding recipients that a vote for the independent candidate in the race, former Scottsdale police Lt. Mike Stauffer, was essentially a vote for Arpaio because it would bleed support from Penzone.

The union-funded group became active in Arizona politics beginning in 2007, said Brendan Walsh, the political-action committee's chairman, after immigration enforcement began to cause concerns for workers' rights.

The emphasis on issues affecting local workers is a key difference between the union funding and the out-of-state donors fueling Arpaio's campaign, he said.

"It's rooted in our local membership and the needs of our local membership," Walsh said. "That certainly does distinguish from Arpaio's national donors, where they don't have a local interest."

Arpaio's campaign manager, Chad Willems, said: "I think the voters of Maricopa County need to ask themselves why a New York-based labor union would pour half a million dollars into a county sheriff's race? What do they have to gain from Penzone being sheriff?"

Though the labor groups have worked on other local campaigns in the last five years, including Phoenix City Council races, their focus has been on registering more than 34,000 new voters and reminding them to vote on Nov. 6, Walsh said. He expects volunteers and workers to knock on 50,000 doors in the coming weeks.

Those doors likely won't include homes in Sun Lakes, a retirement community and Arpaio stronghold where Penzone made an appearance last week to speak with a crowd of about 50 residents, most of them supporters. When Arpaio spoke in the same room earlier this year, it was packed, one resident said.

Still, there are signs of support for Penzone — like those that dot some yards in Sun Lakes.

Arpaio's campaign scoffs at the notion that the race might be close, calling it a fabrication of activists and the media. Poll numbers vary, depending on which candidate paid for the survey. But Arpaio has remained ahead in all of the surveys, with his lead over Penzone ranging from 14 percentage points to about 4 percentage points.

The Penzone campaign, however, paints the monthlong advertising blitz on Phoenix-area television as a sign that Arpaio is sweating.

One ad funded by Arpaio's campaign accuses Penzone of beating his ex-wife. It is based on a 9-year-old police report. The ad came up several times at Penzone's Sun Lakes appearance — Penzone himself offered to answer any audience questions on the topic.

The domestic-violence report came after a 2003 argument between Penzone and his former spouse at her Glendale home. Both ended up with minor injuries, and Penzone was listed as the victim in a police report.

The Glendale prosecutor's office declined to take the case because there was no likelihood of conviction, according to police records.

Penzone is up front about the incident when speaking publicly, and told the Sun Lakes crowd he immediately called his Phoenix police supervisor to disclose the incident. He said any allegations that he pushed his ex-wife are "untrue."

Residents at the meeting said afterward that they would prefer candidates focus on issues related to running the Sheriff's Office instead of personal matters.

"My assumption was, it's just another political lie because Arpaio is threatened," said Sun Lakes resident Pat Murrish. "It's just like most campaigns now."

Pollster Merrill said about 85% of Arizona political ads are negative, but they tend not to have too much impact on the outcome of races. That is particularly true with a candidate like Arpaio, about whom most voters have long-held opinions.

"They can't change people's minds," he said. "They are very effective sometimes in energizing your base, particularly now that we're in the end-game."

The race, Merrill said, could come down to which candidate does a better job getting out the vote.

In that regard, the labor groups' opposition to Arpaio and their commitment to voter turnout could affect the outcome, Merrill said.

"That kind of local effort becomes absolutely crucial and could be a deciding factor in a close race," he said. "And this could be a close race."